An arithmetic processing section is designed to repeatedly execute product-sum arithmetic processing a number of times equal to the number of samples corresponding to each of the frequencies, in which a value obtained by subtracting a product-sum arithmetic value two sampling periods before from an input signal and a value obtained by multiplying a product-sum arithmetic value one sampling period before by a coefficient corresponding to a reference frequency contained in a DTMF signal are added. A comparator extracts an output value equal to or larger than a predetermined threshold value from the product-sum arithmetic values obtained by the arithmetic processing section. A matrix section determines the type of DTMF signal on the basis of at least two output values extracted by the comparator.
Legal claims defining the scope of protection, as filed with the USPTO.
1. An apparatus for receiving and processing a tone signal generated by arbitrarily combining a plurality of reference frequencies, comprising: processing means for processing the reference frequencies so as to and a first reference value for each of the reference frequencies and a second reference value for each of the plurality of reference frequencies and calculate an arithmetic value at current time for each of the reference frequencies, the first reference value being calculated by multiplying the arithmetic value for each of the reference frequencies by a coefficient, which is held in said processing means, before a predetermined period which is n times of sampling periods, wherein n is an arbitrary natural number, the coefficient being determined in accordance with each of the reference frequencies, the second reference value being calculated by subtracting the arithmetic value for each of the reference frequencies from a current tone signal, which is held in said processing means, before 2 times of the predetermined periods, the arithmetic value being obtained by repeating processing of adding the first reference value and the second reference value a number of times equal to a number of samples corresponding to each of the plurality of reference frequencies; output value extraction means for extracting an output value equal to or larger than a predetermined threshold value from the arithmetic values for the respective reference frequencies, which are calculated by said processing means; and signal determination means for determining a type of the tone signal on the basis of at least two output values extracted by said output value extraction means.
2. An apparatus according to claim 1 , wherein said processing means comprises subtracting means for subtracting a signal the 2n sampling periods before from the tone signal at the current time, adding means for adding an output from said subtracting means to a signal before the determined period to output the arithmetic value, first delaying means for delaying an output from said adding means by the determined period, second delaying means for delaying an output from said first delaying means by the determined period and outputting the value to said subtracting means, and multiplying means for multiplying the output from said first delay means by the coefficient corresponding to the reference frequency and outputting the value to said adding means.
3. An apparatus according to claim 1 or 2 , wherein said arithmetic processing means comprises a memory circuit which stores a number of samples and coefficient corresponding to each of the plurality of reference frequencies, and arithmetic control means for controlling said memory circuit sequentially read out and output each number of samples and coefficient from said memory circuit every time arithmetic operation for one reference frequency is ended, and supply the coefficient to said multiplication means to execute arithmetic processing a number of times equal to the number of samples.
4. An apparatus according to claim 1 , wherein said output value extraction means comprises a storing means for storing arithmetic values for all the reference frequencies, which are calculated by said arithmetic processing means, in units of frequencies, and reading means for reading out and outputting an output value equal to or larger than a predetermined threshold value from the product-sum arithmetic values stored in said output holding means.
5. An apparatus according to claim 1 , wherein said signal determination means has a discrimination table in which discrimination data of the tone signal corresponding to sets of two out of all the reference frequencies possibly contained in the tone signal are stored, and discrimination data output control means for reading and outputting corresponding discrimination data from the discrimination table on the basis of at least two output values from said output value extraction means.
6. An apparatus according to claim 1 , wherein said arithmetic processing means, said output value extraction means, and said signal determination means time-divisionally execute processing for each of the plurality of reference frequencies.
7. A tone signal transmitting apparatus for time-divisionally generating a tone signal having a plurality of types of waveforms, comprising: first generation means, having a memory whose information contents are rewritable by an external control signal, for sequentially generating a plurality of types of amplitude information written in the memory; second generation means, having a memory whose information contents are rewritable by an external control signal, for sequentially generating a plurality of types of frequency information written in the memory; third generation means for generating a sine wave signal, as the tone signal on, the basis of the amplitude information output by said amplitude information generation means and the frequency information output by said frequency information generation means; and resetting means for resetting said sine wave generation means at a predetermined interval to stabilize the sine wave signal output for said sine wave generation means.
8. An apparatus according to claim 7 , wherein said reset means comprises counting means for counting an elapse time from reset, detecting means for detecting that a sign of the sine wave signal output from said sine wave generation means changes from positive to negative, and resetting means for resetting said sine wave generation means after a predetermined period in response to the detection signal.
9. An apparatus according to claim 7 , wherein said resetting means forcibly resets said sine wave generation means upon receiving an external reset signal.
10. An apparatus according to claim 7 , further comprising processing means for selectively deriving the sine wave signal output from said sine wave generation means or the amplitude information output from said amplitude information generation means using an output selector for switching in accordance with an external control signal so as to selectively replace an amplitude value of the sine wave signal output from said sine wave generation means with a fixed value.
11. An apparatus according to claim 7 , further comprising processing means which includes: an adder for adding the sine wave signal output from said sine wave generation means and an output from said processing means, an output processor for selectively outputting a first output from said sine wave generation means and a second output from said processing means at a predetermined period, and an output selector for selectively outputting the first output and the second output on the basis of an external control signal.
12. An apparatus according to claim 7 or 11 , further comprising compression means, capable of switching between a first compression rule and a second compression rule for different compression schemes on the basis of an external control signal, for selectively compressing an output from said processing means on the basis of the first compression rule or the second compression rule.
13. An apparatus for receiving and processing a tone signal having arbitrarily combining a plurality of reference frequencies, and generating and transmitting a tone signal having a desired frequency in one of transmission and reception processing modes, comprising: adding means for adding a predetermined first reference value for each of the plurality of reference frequencies and a predetermined second reference value for each of the plurality of reference frequencies within a band of the tone signal to calculate a arithmetic value at current time for each of the plurality of reference frequencies; first delaying means for delaying an output value from said adding means by a determined period which is n times of sampling periods, wherein n is an arbitrary natural number; second delaying means for delaying an output value from said first delay means by the determined period; multiplying means for multiplying the output from said first delay means by the coefficient determined in accordance with a reference frequency to calculate the first reference value for each of the reference frequencies; and calculating means for calculating the second reference value from an output value from said second delay means, wherein in the transmission processing mode, the output value from said second delaying means is set to an initial amplitude value determined in accordance with a frequency of a tone signal to be generated, a coefficient determined in accordance with the frequency of the tone signal to be generated is given to said multiplying means, and the second reference value is generated by said calculating means by inverting the output value from said second delaying means, and in the reception processing mode, an input signal is input to said calculating means, the output value from said second delaying means is subtracted from the input signal to calculate the second reference value for each of the reference frequencies, and the coefficient determined in accordance with the reference frequency is given to said multiplying means.
14. An apparatus according to claim 13 , further comprising a first selector for switching between execution and stop of processing of setting the output value from said second delaying means to the initial amplitude value determined using the frequency of the tone signal to be generated in accordance with the tone signal transmission processing mode, a second selector for switching the coefficient to be given to said multiplying means in accordance with the transmission processing mode or the reception processing mode, and a third selector for switching between execution and stop of processing of giving the input signal to the calculating means in accordance with the transmission processing mode or the tone signal reception processing mode.
15. An apparatus according to claim 14 , wherein said first, second, and third selectors alternately switch at a predetermined period.
16. An apparatus according to claim 13 , further comprising peak extraction means for, in the reception processing mode, extracting a peak value equal to or larger than a predetermined threshold value from the arithmetic values calculated by said adding means for the respective reference frequencies, and signal determination means for determining a type of the tone signal on the basis of at least two peak values extracted by said peak extraction means.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
November 22, 2000
December 23, 2003
Browse 5M+ US patents with plain-English claim translations and AI-generated analysis.